The present invention generally relates to image forming apparatuses, and more particularly to an image forming apparatus which is provided with a means for detecting a transport abnormality (paper jam) in a paper transport path and for stopping a sequential operation of image formation.
Generally, in image forming apparatuses such as printers including laser printers, copying machines and facsimile machines, a sequence control part which uses a microcomputer controls the sequential operation of the image formation. In addition, a plurality of paper transport paths are provided in the image forming apparatus to supply the paper and to eject the paper after the image formation.
A sensor is arranged in each paper transport path and functions as a paper detecting means for detecting the paper which passes through the paper transport path. Hence, while the sequential operation is controlled by the sequence control part, it is possible to detect a transport abnormality, that is, a paper jam, based on output signals of the sensors. When the paper jam is detected, the sequential operation is stopped by the sequence control part so as to stop the paper transport. In addition, a message indicating the generation of the paper jam is displayed on a display part which is provided on an outer side of a main apparatus body of the image forming apparatus. Among such image forming apparatuses, there are image forming apparatuses capable of also displaying the position where the paper jam is generated.
In order to restart the image forming apparatus the sequential operation of which is stopped by the generation of the paper jam, a front or side cover of the image forming apparatus is opened to remove all the papers causing the paper jam. Then, a reset button is pushed to make a reset operation which cancels both the stopped state of the sequential operation and the display on the display part. Alternatively, the reset operation may be made automatically when the front or side cover is closed.
However, according to the conventional image forming apparatus, it is impossible to know how many sheets of paper remain within the image forming apparatus when the paper transport is stopped by the generation of the paper jam. As a result, not all the sheets of paper within the image forming apparatus may be removed when eliminating the paper jam. For this reason, there is a problem in that it is often necessary to repeat the operation of removing the sheets of paper within the image forming apparatus when the paper jam occurs because not all the sheets of paper may be removed in one removing operation.
On the other hand, after the paper jam is eliminated, it is sometimes difficult to determine the page from which the printing, copying or facsimile transmission is to be resumed.
When the transport abnormality is generated at an ejecting part of the image forming apparatus, the paper transport is often stopped in a state where a tip end of the paper projects from a paper ejecting opening of the ejecting part. In this case, the paper causing the transport abnormality, that is, the paper jam, may be removed by simply pulling the tip end of the projecting paper in a paper ejecting direction. But in the conventional image forming apparatus, the front or side cover must be opened and closed or the reset button must be pushed in order to make the reset operation and restart the sequential operation of the image forming apparatus even though the paper jam is eliminated by the operation of simply pulling out the paper from the paper ejecting part. As a result, there are problems in that a troublesome operation must be carried out to restart the sequential operation and it takes time for the image forming apparatus to resume the sequential operation.
Furthermore, the stopped state of the sequential operation cannot be cancelled unless all the sheets of paper within the paper transport path are removed and the reset operation is made. This means that even when a certain transport path is usable when the paper jam occurs in another transport path, the certain transport path cannot be used for the image formation until the paper jam is eliminated and the reset operation is made. Therefore, in this case, there is a problem in that the efficiency of the image forming apparatus is poor.